Fabrics treated with chromium compounds

ABSTRACT

COMPOSITE FABRIC FOR USE AS CONVEYOR BELTING AND THE LIKE IS MADE BY RESIN-IMPREGNATING AND BONDING A TEXTILE FABRIC WHICH CONTAINS ORGANIC SYNTHETIC FIBERS, SUCH AS NYLON. THE SYNTHETIC FIBERS EITHER BEFORE OR AFTER INCORPORATION IN THE TEXTILE FABRIC ARE TREATED WITH AN AQUEOUS SOLUTION CONTAINING IONIC CHROMIUM TO IMPROVE FIRE RESISTANCE AND ADHENSION BETWEEN THE SYNTHETIC FIBERS AND THE RESIN.

United States Patent US. Cl. 156-333 Claims ABSTRACT OF THE DISCLOSURE Composite fabric for use as conveyor belting and the like is made by resin-impregnating and bonding a textile fabric which contains organic synthetic fibres, such as nylon. The synthetic fibres either before or after in corporation in the textile fabric are treated with an aqueous solution containing ionic chromium to improve fire resistance and adhesion between the synthetic fibres and the resin.

This invention is concerned with improvements in or relating to fabrics, and is particularly concerned with fabrics comprising a combination of a textile fabric and a resinous composition. More particularly, though not exclusively, the invention relates to such a fabric for use as conveyor belting, power transmission belting or the like.

Belts have been described, particularly belts for use in the conveyance of coal, which comprise several plies of a textile fabric bonded together by means of a rubber or synthetic resin composition and which have a surface composed of the said composition.

The advantages of using synthetic fibres, such as nylon 66 (polyhexamethylene adipamide), as opposed to natural fibres, such as cotton, for making the textile fabric, particularly those accruing from better tensile strength, extensibility, impact resistance and abrasion resistance, have long been recognised. However, belting made from fabrics constructed wholly or mainly from synthetic fibres has, from time to time, been subject to criticism on the grounds of poor adhesion between the synthetic fibre and the bonding composition and greater inflam.- mability of such belting compared with that made using natural fibres such as cotton.

One of the various objects of the present invention is to produce a composite fabric as described, wherein the advantages of synthetic fibres are exploited and whereis there is, at the same time, satisfactory adhesion between the synthetic fibre and the bonding composition and satisfactory flame resistance.

It has been found that this object can be accomplished by treating the synthetic fibres. either before or after conversion into a fabric, with chromium compounds.

According to the present invention an improved composite fabric is produced from an assembly of one or more layers of a textile fabric comprising synthetic fibres, treated with one or more chromium compounds and impregnated and bonded with a resinous composition to form an integral fabric.

The term chromium compound comprises both inorganic compounds, where the chromium is present in the anionic or cationic state e.g. sodium bichromate, chromic chloride or chrome alum, applied alone or in combination with chrome dyestuffs, or organic compounds such as premetallised dyestuffs containing chromium.

Experiments have shown that the dyestuffs mentioned above confer increased adhesion between the synthetic 3,573,134 Patented Mar. 30, 1971 fibre and the bonding composition, although the reason for this is not known.

The improvement in flame resistance is believed to be in some way connected with the treated fibre charring when a flame is applied to it, with formation of an ash-like surface, such as happens with cotton, rather than melting and constantly exposing a fresh surface.

The fabric may be of any appropriate construction, for instance a twill weave or a plain weave. It may be made entirely from synthetic fibres such as polyamides, for example polyhexamethylene adipamide or polyhexamethylene sebacamide, polyesters such as polyethylene terephthalate or polyacrylics such as that sold under the registered trademark Orlon. It may contain in addition to the synthetic fibres a proportion of other fibres such as cotton to produce advantageous blends.

The bonding composition may consist of any mixture of a suitable resinous material, such as polyvinyl chloride, together with suitable plasticizers, pigments, fillers or the like.

In order that the invention may be fully understood, examples thereof will now be described with particular reference to the manufacture of conveyor belts. In general, such methods comprise coating one or several layers of a textile fabric with a suitable resinous composition after which they are superimposed to make an integral structure and the resinous composition then cured by, for instance, a heat treatment. The belt is finished by pressing.

The present invention is illustrated but in no way limited by the following examples:

EXAMPLE I In this example, two fabric constructions were used. One fabric (identified hereinafter as fabric A) was plain woven with a warp comprising 24 ends per inch of 6 fold 840 denier poly(hexamethylene adipamide) filaments and a weft of 12 picks per inch of 3 fold 840 denier poly(hexamethylene adipamide) filaments. The other fabric (identified hereinafter as fabric B) was in the form of a broken twill weave comprising a warp of 20 ends per inch of 3 fold 840 denier poly(hexamethylene adipamide) filaments each and 12.5 picks per inch of 4 fold 840 denier poly(hexamethylene adipamide) filaments.

The two fabrics, 'it will be noted, were constructed entirely of the synthetic fibre poly(hexamethylene adipamide)-nylon 66.

Pieces of each of the fabrics were dyed with the chrome dyestutf Eriochrome Black T150, in the normal manner. The actual procedure was essentially as follows:

The fabric was immersed in an aqueous, slightly acid dye bath containing 8% of the dyestuff and boiled for about 2 hours. After this it was rinsed and then boiled for 1 hour in an aqueous solution of 4% sodium dichromate 1% formic acid. Finally it was thoroughly washed and dried.

Each piece of fabric was then coated on both sides by spreading with polyvinyl chloride paste of the formulation given below:

a tribasic lead sulphate 3 /2 Pigment 1 The resulting ducks were cut out to an appropriate size and then made up into two (one for each fabric) 3 ply belt samples in an electrically heated and water cooled press.

Two other belts of identical construction (and hereinafter referred to as Control A and Control B respectively) were made up from other portions of the initial fabric but, in this instance, the dyeing treatment was omitted.

The four belts were then tested according to the National Coal Board Specification No. 158/1960 for adhesion to the resilient resinous (polyvinyl chloride) composition and flame resistance.

The results are tabulated below:

Ply to ply Residual adhesion, burning lb./inch time, secs.

Control Fabric A 6 60 Treated Fabric A 22 4. 6 Control Fabric B. 60 Treated Fabric B 53 1. 3

It will be observed from the results given that in respect of adhesive capacity and flame resisance the two fabrics which had been subjected to the dyeing process as a means of effecting surface modification of the poly(hexamethylene adipamide) yarns in the fabrics were superior to the control fabric.

EXAMPLE II The procedure of Example I was followed except that the treatment to effect modification comprised padding into the fabrics sodium chromate at two different concentrations and at a temperature of 40 C. after which the fabrics were dried at a temperature of 80 C.

The results in respect of adhesive capacity and flame resistance are tabulated below:

Fly to ply Residual EXAMPLE III A piece of fabric of identical construction to Fabric B used in Example 1 hereinbefore was dyed in the normal manner with Amichrome Light Black RBLL (Dye & Chemical Alliance Co. Ltd.), a chromium-containing premetallised dyestuif.

This was done by immersing the fabric in a dyebath containing 8% of the dyestuff and 1% acetic acid, at 50 C., bringing to the boil over 30 minutes and boiling for 1%. hours. After this the fabric was thoroughly washed and dried.

The dyed fabric made up into a 3 ply belt using the technique described in Example 1. The adhesive capacity and flame resistance of the fabric were measured and compared with a belt constructed from identical fabric What we claim is: 1. A process for the production of a composite fabric having a textile fabric assembly bonded with a resinous composition, said process comprising: applying to organic synthetic fibres an aqueous solution of a chromium compound in which the chromium is in the ionic state in order to improve the adhesion between said fibres and the resinous composition in the composite fabric and in order to improve the flame resistance of the composite fabric; thereafter incorporating the fibres in a textile fabric assembly; and impregnating and bonding the textile fabric assembly with a resinous composition.

2. A process as claimed in claim 1 wherein the synthetic fibres comprise polyamides.

3. A process for the production of a composite fabric having a textile fabric assembly bonded with a resinous composition, said process comprising: incorporating organic synthetic fibres in a textile fabric assembly; improving the adhesion between said fibres and the resinous composition in the composite fabric and improving the flame resistance of the composite fabric by applying to the textile fabric assembly an aqueous solution of a chromium compound in which the chromium is in the ionic state; and thereafter impregnating and bonding the textile fabric assembly with a resinous composition.

4. A process for the production of a composite fabric having a textile fabric assembly bonded with a resinous composition, said process comprising: incorporating organic synthetic fibres in a textile fabric assembly; improving the adhesion between said fibres and the resinous composition in the composite fabric and improving the flame resistance of the composite fabric by applying to the textile fabric assembly an aqueous solution of a chromium compound in which the chromium is in the ionic state; assembling a plurality of layers of the treated textile fabric assembly; and thereafter impregnating and bonding the textile fabric assembly with a resinous composition.

5. A process as in claim 3 wherein the chromium compound is selected from the group consisting of alkali metal dichromate, chromic chloride, chrome alum, Eriochrome Black and Amichrome Black.

6. A process as in claim 4 wherein a major part of the textile fabric assembly is constructed of said organic synthetic fibres.

7. A process as in claim 6 wherein said organic synthetic fibres are selected from the group consisting of polyamide fibres and polyester fibres.

8. A process as in claim 3 wherein the textile fabric is constructed only of fibres selected from the group consisting of said organic synthetic fibres and mixtures thereof with natural textile fibres.

9. A process as in claim 4 wherein the textile fabric is constructed only of fibres selected from the group consisting of said organic synthetic fibres and mixtures thereof with natural textile fibres.

10. A process as in claim 8 wherein said organic synthetic fibres are polyamide fibres wherein said resinous composition is polyvinyl chloride and wherein the chromium compound is an ionic chromium salt.

References Cited UNITED STATES PATENTS 2,650,184 8/1953 Biefeld 154-120 2,744,835 5/1956 Caroselli 117--72 3,023,072 2/1962 Dabrowski 882 FOREIGN PATENTS F. B. Hauserman: Chromium Complexes, reprint Advances in Chemistry Series, No. 23 (1959), pp. 338, 345, 348, 353, 354.

NORMAN G. TORCHIN, Primary Examiner R. E. FICH'DER, Assistant Examiner U.S. Cl. X.R. 

